Rise and Fall of Agamemnon---- Biplane Swing Wing Boost Glider

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BABAR

Builds Rockets for NASA
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Been built and flown. Concept I think is valid although did not have a successful flight..
Figured I'd document the build so people can offer me suggestions and also might give some other people some ideas.

These are the pics with the wings stowed in boost configuration

IMG_2478.jpgIMG_2480.jpgIMG_2481.jpgIMG_2485.jpgIMG_2486.jpg
 
[video=youtube;NY6CV9GDQmI]https://www.youtube.com/watch?v=NY6CV9GDQmI&feature=youtu.be[/video]

Winds light.

D12-3 Engine.

Hard to see on video but a very straight boost with almost no roll.

Deployment at Apogee.

The wings are pulled forward by rubber bands (similar to many helicopter blades). At the last minute I double the rubber bands for redundancy and for extra pull......................... Good idea in theory, but------ the wings are meant to go from parallel to the fuselage to 90 degrees at deployment. They are "stopped" by kevlar tethers, which attach to a "strut" along the anterior aspects of the wings (well, anterior when deployed, lateral when stowed.) The strut not only provides a place of attachment for both the pull bands forward and the tethers in back, but they also serve to keep the upper and lower wings "spread" or separated.

The tethers are attached to the "displacers" which hold the rubber band "pulls" away from the fuselage. This gives a better "moment" or angle of pull at the beginning of swing wing deployment (pulls them "out" and away from the fuselage initially, then the bands can swing the wings forward.) The "displacers" (they look like canards about one fourth distance forward of tail) were glued to the side of the fuselage which was made of posterpaper. The extra force of the "doubled" rubber bands pulled so hard on the tethers that it ripped the tethers with the displacers of the side of the paper (really dumb of me, didn't even think that was a potential site of structural failure.)
The wings swept forward beyond 90 degrees, about to 150 degrees. You can see the "Y" configuration as the rocket tumbles safely to the ground.
 
First pic shows the displacer ripped off and the wings swept WAAAAAY to far forward.

Second pic shows where it SHOULD be

Ripped off Displacer.jpgDisplacer in position.jpg
 
This is an engine eject model. There is room to put a streamer around the engine, something strongly recommended in areas where there is a fire danger.

With the engine in place, the elevator is held in a neutral position. When the engine ejection fires, it burns a rubber band which crosses the fuselage just anterior to the engine. The rubber band (actually two rubber bands tied together, one wasn't long enough) loops through the fuse AND through holes in the ends of the stowed upper and lower wings. The band then sweeps back posteriorly along the superior and inferior surfaces of the glider fuselage and wraps around the engine. This "burn band" therefore holds the stowed wings AND hold the engine in place. It also passes over the elevator. However, the elevator has rubber bands on each side of it with pull it up against the fuselage (and the engine, when in place.) THESE bands pass over the horizontal stabilizers. The stabilizers have a dihedral to help stability.

When the engine deployment charge first, it burns the "burn band", releasing the wings AND releasing the engine. The force of the ejection also kicks the engine out the back. Once the engine is kicked out, the side bands pull the elevator toward the fuselage. The sides of the fuselage have angled "stops" to stop the elevator motion at about 10 degrees.Tail Engine In.jpgTail Engine Out.jpg
 
The central axle is a BT-5 body tube.

I used BT-5 to BT-20 centering rings make the contact points for the wings. I cut holes just slightly smaller than the BT-20 size where I wanted them. I then used rolled up sandpaper around a mini-engine casing to sand the insides of the holes to where it would just BARELY fit the centering rings. Then stuffed the centering rings in the holes and glued them to the balsa wings.

I cut pieces of plastic "hotel key" cards and attached them to the posterboard fuselage for strengh. I cut BT-5 holes in the cards on top and bottom to provide a pathway for the axle, which runs from top to bottom through the fuselage. The uppermost UPPER wing and the lowermost LOWER wing are on ONE side (these are the farthest away from the fuselage above and below.) The other wings (the lowermost UPPER wing and the uppermost LOWER wing, if you will) make up the OPPOSITE side. Why? Because I could permanant attach the uppermost and lowermost (aka the OUTERMOST) wings to the axle, holding the other INNERMOST wings on the inside. This is because with both outermost wings attached to the axle, they can swing together, and I didn't need an extra "cap" on the top or the bottom.IMG_2440.jpg
 
For the second flight, I used both transverse ties of kevlar woven through the fuselage and the "displacers" to hold them in place, and added Kevlar attachments from "displacers" to the tail. Made darn sure those weren't going to come off again.

Calm winds--- really a perfect day for a flight.

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D12-3 Engine.

Perfect booost.

Ejection charge fired just a bit after apogee.

.................................................................................................:eyepop:

................................................................................................:eyepop:
wings didn't release:y::cry:

Nosed gentle over and started picking up speed.

Would have been a lawn dart...... except for the asphalt.
On the good side, there was not another person in sight to witness the extremely rapid deceleration.

Ironically, although it hit nose first, the rocket actually bounced and (I kid you not) flipped over and "stuck" the landing on the tail.:facepalm:
 

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I try to (and usually do) learn from failures. In this case, I am not SURE why the wings failed to deploy (since they did deploy correctly with the first flight.) I am thinking maybe some gunk from the first ejection charge may have gummed up the pathway for the burn band, and therefore it burned but didn't "pull out". The one wing hanging out drunkenly on the landing picture was clearly released AFTER impact, as I watched it come in. So lesson learned there is to make sure the pathway is clear before each flight--- probably need a more secure "fixed" edge for the band to wrap around as it comes throught the outermost upper and lower wings.

Lesson from flight one--- don't make "last minute" changes without completely considering (and preferably preflight testing) their effect. The deployment system worked perfectly with one set of bands on each wing pair before flight one, the extra bands were too much for the tether/displacer attachments to hold. Of course, the real failure was not realizing how much stress was placed on those attachments.

I think there is potential for "square bodied" swingwing gliders. Although a square cross sectional diameter is has more drag than a round one, by tucking the wings in against the square diameter I think it reduces the amount of drag during boost phase otherwise created by the wings "draped" over a round body tube. In fact, on the first flight on the D12-3, I think deployment was bit early on review of the video--- somewhat surprising with all that "nooks and crannies" from the winglets and the tail assembly.

I am NOT sure about how well the "biplane" concept will work. The Agamemnon had a "swollen" midsection to allow me to attach the upper and lower wings further apart. My next version will be simpler (should have started with it) as a minimum diameter 24mm, meaning the upper and lower wings will only be about 1" apart. I don't know the effect that will have on the airflow and lift---- obviously Eddie Rickenbacker and company proved Biplane work quite well, but the wings on those birds were several FEET apart.

It would be possible to have two separate hinges so the upper level and lower level wings were not right next to each other, but adds a more complexity.

Anyway, for any and all that read this far, thanks, and please share you ideas.

Tom
 
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Very creative, I like the idea of the wing tips being fins at liftoff, nice outside the box thinking ! I've been fumbling with a swing wig design for the last year or so--nothing cut or glued yet--I took a little diferent approach. I planned on using basswood leading edge strakes to stop the wing as it swung forward. The wings would be pulled forward by the wing root--pulled backwards by elastic or rubber. Funny how we all come up with different approaches to problems and manage to work them out. --H
 
Yup it's always the little things that get ya. Tried my hand at designing a swing wing and the (probably over-stretched) elastic broke the fuselage at deployment. Also the geometry of the elastic routing path turned out to be not quite right and sometimes it would slip off and not deploy the wings. Then there was that severe spin when launched (something is misaligned but I just haven't found what it is yet). It looked great on paper and when trimmed but all the minor things added up to something that needs a major reworking.


The proximity of the wings to one another may not be all that critical if you opt to use a 24mm tube. I came across an NAR research summary on Bi- and Tri-wing glider research and the prototype models used had wings that were pretty close together. (I can forward you the pdf article/plans if you're interested if you PM me your email addy).
 
Forgot to ask a question: What keeps the rubber band from slipping off the narrow edge of the "displacers"? In helirocs half a launch lug mounted to the tip of the rotor dihedral stop serves to hold the rubber band in place. I couldn't see what serves that function in your pics.
 
Forgot to ask a question: What keeps the rubber band from slipping off the narrow edge of the "displacers"? In helirocs half a launch lug mounted to the tip of the rotor dihedral stop serves to hold the rubber band in place. I couldn't see what serves that function in your pics.

First, all my “displacers” and/or rotor stops are bilaminar or trilaminar. If bilaminar usually two pieces 1/8” balsa, with grain directions 90 degrees opposed, best is DIAGONAL (45 degrees) of axis of rocket. Once glued/laminated these are strong on any stress axis.

If trilaminar, the outside pieces have grain perpendicular to long axis of rocket, inside piece grain parallel.

If bilaminar, before you glue, put bevels on each outside margin. When you glue them, bevels face each other to make a v shaped trough. Drizzle thin CA after laminating for strength. Reason for 45 degree angle is so neither piece is parallel to the band (would break off really easily.)

Currently most of mine are trilaminar 1/16”. The middle piece is cut a shorter on width axis, so when glued together there is again a “trough” or canal that holds the band or string. Outside pieces are perpendicular to the band for strength purposes.

You can laminate/glue these with either wood glue or thick Ca. If wood glue, you need to stick them between wax paper and put them in a book or something to keep them flat and together, otherwise they warp. With thick CA you can just stick them in a clothes pin.
 
First, all my “displacers” and/or rotor stops are bilaminar or trilaminar. If bilaminar usually two pieces 1/8” balsa, with grain directions 90 degrees opposed, best is DIAGONAL (45 degrees) of axis of rocket. Once glued/laminated these are strong on any stress axis.

If trilaminar, the outside pieces have grain perpendicular to long axis of rocket, inside piece grain parallel.

If bilaminar, before you glue, put bevels on each outside margin. When you glue them, bevels face each other to make a v shaped trough. Drizzle thin CA after laminating for strength. Reason for 45 degree angle is so neither piece is parallel to the band (would break off really easily.)

Currently most of mine are trilaminar 1/16”. The middle piece is cut a shorter on width axis, so when glued together there is again a “trough” or canal that holds the band or string. Outside pieces are perpendicular to the band for strength purposes.

You can laminate/glue these with either wood glue or thick Ca. If wood glue, you need to stick them between wax paper and put them in a book or something to keep them flat and together, otherwise they warp. With thick CA you can just stick them in a clothes pin.

Clever method, and again a solution to more than a single requirement. Great idea to pigeonhole for a possible use in one of my future builds, thanks, very cool and valuable tip!
 
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